Johnson, Erik; Johnson, Ellie; Johnson; Jerald (Brigham Young University)
Faculty Advisor: Johnson, Jerald (Brigham Young University, Biology)
It seems counterintuitive that organisms should evolve handedness (or what we might more broadly refer to as "lateralization"). Individuals who can forage equally well with both hands, who can kick equally well with both feet, who can detect stimuli and orient equally well in both directions, and so on—these individuals should be favored relative to those who are either right handed or left handed. Yet in humans, and in several other species, handedness is common, but we still no very little about why. Here we explore this question using a tropical freshwater fish species with an unusual anatomy. Males have a modified fin—the gonopodium—that they use to internally inseminate females. Interestingly, males are either right or left handed for this structure, which terminates with either a dextral or sinistral twist. In this study, we ask a simple question: is there a link between male gonopodium morphology and male behavioral lateralization. We use a detour test approach to determine how males approach different stimuli, turning either to the left or right to more clearly see each type of stimulus. We focus on how males approach potential mates, predators, and novel items. We predict that males with a dextral gonopodium will orient differently than those with a sinistral gonopodium, consistent with the idea that there is link between behavioral lateralization and morphological handedness. If true, it would suggest that reproductive morphology could be linked to brain and behavioral lateralization in vertebrates.